<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>  </title>
</head>
<body>
    
</body>

<script>
    var a = [ "America", "Greece", "Britain", "Canada", "China", "Egypt"];
    console.log(a.indexOf("a"));
</script>
</html>